For a defensive heavy, Brass Beast. For an offensive heavy, maybe a Brass Beast, or definitely consider a Tomislav (that's one of the new weapons). For melee, most people run either Gloves of Running Urgently, or something steel fists. Secondary weapon is default Shotgun, Sandvich is good too.
Pyro, Backburner is great if you are into defense and can get behind your enemy (i.e. dropping down). Degreaser is good, it gives faster weapon switches at the cost of afterburn damage. For your secondary, Detonator is an improved Flare Gun, I still like Shotgun for reliable classic damage. As for the melee, you have a ton of options. If you like combat, probably a Back Scratcher, or if you use Flamethrower/Degreaser, consider the Axtinguisher. If you do defense, Homewrecker to deal with spies.
Sniper, Sydney Sleeper isn't bad, especially if you struggle for headshots. Huntsman is good for close combat or luck. Razorback protects from spies, Jarate is helpful sometimes.